21728806 has 16 divisors (see below), whose sum is σ = 35653968. Its totient is φ = 9849600.

The previous prime is 21728789. The next prime is 21728807. The reversal of 21728806 is 60882712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21728807) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8386 + ... + 10666.

It is an arithmetic number, because the mean of its divisors is an integer number (2228373).

Almost surely, 2^21728806 is an apocalyptic number.

21728806 is a deficient number, since it is larger than the sum of its proper divisors (13925162).

21728806 is a wasteful number, since it uses less digits than its factorization.

21728806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2727.

The product of its (nonzero) digits is 10752, while the sum is 34.

The square root of 21728806 is about 4661.4167374308. The cubic root of 21728806 is about 279.0478115070.

It can be divided in two parts, 21 and 728806, that added together give a palindrome (728827).

The spelling of 21728806 in words is "twenty-one million, seven hundred twenty-eight thousand, eight hundred six".